The invention is directed to a process for the production of a cyanocarboxylic acid by reacting a halocarboxylic acid with a substance yielding cyanide ions. The invention is particularly concerned with a process for the production of cyanoacetic acid from chloroacetic acid.
It is known to produce cyanoacetic acid by the action of cyanides and chloroacetic acid. For this purpose the chloroacetic acid in the presence of water is converted by means of sodium carbonate into its sodium salt, this is reacted with sodium cyanide and subsequently the reaction mixture is acidified. The water free cyanoacetic acid is recovered from this mixture which besides water contains inorganic salts by extraction with ketones having 4 to 5 carbon atoms, methyl isobutyl ketone or mesityl oxide (Britton U.S. Pat. No. 2,338,834 and Nicholl, U.S. Pat. No. 2,480,380) or first is freed from water under reduced pressure and then is extracted with aliphatic esters (Lonza, British Pat. No. 824,640). The disadvantage of these processes is that side products are formed which can only be removed with difficulty so that a cyanoacetic acid obtained by these processes contains undesired impurities and is colored.
It is also known to carry out the reaction in the presence of alkanols such as n-butanol (German OS No. 1930080). This process chiefly serves for the production of the corresponding ester of cyanoacetic acid.